Malapropism is the mistaken use of a word in place of a similar-sounding one, often with unintentionally amusing effect. It often occurs in ordinary speech. Malapropism is also called a malaprop or dogberryism. Malapropism reveals that the English language is complex because it is easy to mistake two words for each other.
Officer Dogberry said, "Our watch, sir, have indeed comprehended two auspicious persons" (apprehended two suspicious persons)